Dung Beetle (Coleoptera: Scarabaeinae) Community Structure Across a Forest-Agriculture Habitat Ecotone in South Western Ghats Thomas Latha1,*, Thomas K
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International Journal of Environment, Agriculture and Biotechnology (IJEAB) Vol-3, Issue- 5, Sept-Oct- 2018 http://dx.doi.org/10.22161/ijeab/3.5.41 ISSN: 2456-1878 Dung beetle (Coleoptera: Scarabaeinae) community structure across a forest-agriculture habitat ecotone in South Western Ghats Thomas Latha1,*, Thomas K. Sabu2 1Department of Science, Faculty of Science and Technology, University of Belize, Belize 2Post Graduate and Research Department of Zoology, St. Joseph’s College, Devagiri, Kozhikode, Kerala, India *Corresponding Author: [email protected] Abstract— Ecotones are zones of transition between biomes positive attribute, as original species composition is altered or ecosystems. Ecotones, natural or anthropogenic, can to favor disturbance adapted species in the region. greatly affect insect community structure across habitats. Keywords— Agriculture habitat, community structure, Scarabaeinae dung beetles are ideal biological indicators dung beetles, ecotone, forest, heliophiles, synanthropic that are used to study effects of habitat modification, species, South Western Ghats. fragmentation and edge effects on biodiversity. Dung beetle community structure across a forest-agriculture habitat I. INTRODUCTION ecotone in South Western Ghats, a biodiversity hotspot in Deforestation over the past half century, has resulted in the India was studied. Dung baited pitfall traps were used to loss of more than a third of all forest cover worldwide collect dung beetles from forest, ecotone and agriculture (Hansen et al., 2013). Nearly 70% of the world’s remaining habitat. Community attributes such as species richness, forests, lies within 1km of an edge and is in close proximity abundance, diversity, indicator and detector species were to human modified landscapes. These forest ecosystems are recorded in the study sites. Species composition varied influenced by human activities, altered microclimate, and between the three habitats. Greater similarity in species non-forest species invasion (Haddad et al., 2015). Reduced composition was observed between forest and ecotone. This fragment area, increased isolation, and increased edge, is attributed to the presence of heliophilic species in the initiate changes in the forest ecosystems which can have region, adapted to survive in forest and the open edge. unpredictable outcomes (Haddad et al., 2015). Though forest recorded higher abundance, ecotone and Anthropogenic edges created by habitat fragmentation agriculture habitat recorded higher species richness and affects biodiversity across ecotones (Laurance, 2000; diversity. Low diversity in forest resulted from decreased Murcia, 1995; Risser, 1995). Ecotones are zones of transition equitability in the overall forest assemblage resulting from between biomes or ecosystems (Hansen and di Castri,1992). increased dominance of few species such as Onthophagus Ecotones can be sharp or gradual and is characterized by furcillifer and O. pacificus. Higher species richness in unique sets of environmental conditions dissimilar from the ecotone and agriculture habitat was associated with adjacent habitats, collectively called edge effects (Murcia, heliophilic species that responded positively to disturbance, 1995). The intensity and direction of edge effects on whereas stenotopic species adapted to closed canopy such as population level of organisms can be extremely variable Ochicanthon mussardi was negatively affected in the region. across species. Different species respond positively, Onthophagus furcillifer, the indicator species in the forest negatively or neutrally to edges (Murcia, 1995; Baker et al., and ecotone was also the detector species in agriculture 2002). habitat. Presence of such species in the region that are Invertebrates such as insects has important functional role to adapted to survive in widely different habitat types is a result play in an ecosystem. Ecotones natural or anthropogenic, can of decades of forest degradation and fragmentation in the greatly affect insect abundance and diversity (Didham et Western Ghats which led to the establishment of heliophiles al.,1996); faunal movement (Yahner, 1988; Wiens et and synanthropic species in the region. Such increase in al.,1995, 1997; Desrochers and Fortin, 2000); population species richness in disturbed habitat is not considered a dynamics (Leopold, 1933); species interactions and www.ijeab.com Page | 1879 International Journal of Environment, Agriculture and Biotechnology (IJEAB) Vol-3, Issue- 5, Sept-Oct- 2018 http://dx.doi.org/10.22161/ijeab/3.5.41 ISSN: 2456-1878 community structure (Didham et al.,1998). Scarabaeinae The vegetation in the forest habitat is characterized by west dung beetles are a group of predominantly dung feeding coast semi-evergreen forest consisting of a mixture of detritivorous beetles, abundant and widely distributed in the evergreen and deciduous trees (Kerala Forests and Wildlife terrestrial ecosystems (Halffter and Mathews, 1966). Department, 2004). Mammalian fauna in the region consists Through their dung feeding and dung burial activities, they of Elephas maximus Linnaeus, 1758 (elephant), Bos gaurus increase soil fertility (Bertone, 2004; Bang et al., 2005; Smith, 1827 (gaur), Cervus unicolor Kerr, 1792 (sambar Losey and Vaughan, 2006), soil permeability (Bang et al., deer), Sus scrofa scrofa Linnaeus, 1758 (wild boar), 2005); plant growth (Galbiati et al., 1995, Bang et al., 2005); Semnopithecus sp.(langur), Macaca silenus silenus seed dispersal (Andresen and Levy, 2004) and control Linnaeus, 1758 (lion tailed macaque), Martes gwatkinsii populations of disease causing parasites (Hingston, 1923; Corbet and Hill, 1992 (Nilgiri marten), Petinomys Miller et al., 1961).They are ideal biological indicators that fuscocapillus Jerdon, 1847 (small Travancore flying are effectively used to study the effects of habitat squirrel), Herpestes fuscus Thomas, 1924 (brown modification, fragmentation and edge effects on biodiversity mongoose), Viverra megaspila Blyth, 1862 (Malabar civet) (Duraes et al., 2005; Feer, 2008; Filgueiras et al., 2015; (Kerala Forests and Wildlife Department, 2004). The study Klein, 1989; Nichols et al., 2008; Spector and Ayzama, sites consisted of a 971 hectare reserve forest, 372 hectare 2003). agriculture habitat of banana and orange plantations and a The Western Ghats in the Indian subcontinent is one of the well-defined ecotone separating the two habitats, 34 biodiversity ‘hotspots’ of the world (Myers , 2003; characterized by scattered trees and less undergrowth. Traps Mittermeier et al., 2004). Nearly three-fourths of the natural were placed in the reserve forest, ecotone and in the portion vegetation in the ecoregion are cleared or converted. Due to of the agriculture habitat with the banana plantation (Fig. 2). their fragility, biological richness, high rates of endemis m 2.2 Sampling and multiple anthropogenic threats, the remaining severely Dung beetles were collected using dung baited pit fall traps fragmented forests of the Western Ghats are of major in the year 2007-08. Three collections were made during the conservation priority on a global scale (Pascal, 1991). There study period (monsoon, presummer, summer). Each is very limited information on effects of habitat collection effort involved placing ten traps each in the three fragmentation and creation of anthropogenic edges on habitats (forest, ecotone and agriculture habitat). Traps were ecologically important insect communities in the region. In placed along ten transverse transects. Each transect was the present study, dung beetle community structure attributes composed of three traps, one trap was placed in forest, one in such as species richness, abundance, species composition ecotone and one in agriculture habitat. The traps were and diversity was investigated across a forest-agriculture separated by a distance of 50 m. Each transect was separated habitat ecotone in South Western Ghats. We hypothesize that by a distance of 50 m. Traps were baited with 200g fresh cow dung beetle community structure attributes will vary across dung. A 25 x 25 cm plastic sheet was set over each trap to the habitats. protect it from rain and sun. The trap contents were collected at 12 h interval (6:00-18:00h and 18:00-6:00h). The collected II. MATERIALS AND METHODS beetles were identified to species levels using taxonomic 2.1 Study site keys available in Arrow (1931) and Balthasar (1963 a, b) and The study site Nelliampathi is located on the “edge” of also by verifying with type specimens available in the Palghat gap in South Western Ghats (Pearson and Ghorpade, Coleoptera collections of St. Joseph’s College, Devagiri, 1989). The collection site Kaikatty in Nelliampathi is located Kozhikode. at 100 31’N longitude and 760 40’E latitude, at an elevation 2.3 Data analysis of 960 msl (Fig. 1). Though extensive in area, Nelliampathi For the purpose of data analysis, the diurnal and nocturnal forests presents a fragmented landscape interspersed by large collections and the three seasonal collections for each habitat number of plantations, dams, and roads. It is an ecologically were pooled. Sample based species accumulation curves high sensitive area forming a corridor for the movement of were plotted for each habitat to assess sampling adequacy long ranging species such as Panthera tigris Linnaeus, 1758 (Gotelli and Colwell, 2001). Nonparametric species richness (tiger), Panthera pardus Linnaeus, 1758 (leopard), Bos estimator Chao 2 was used to compare observed species gaurus Smith, 1827